Maybe because the Falcons were supposed to be a purely air combat machine, and of course, they wanted to stick bombs on it.Years ago I worked with a guy who was a F4 backseater in the Indiana ANG in Ft Wayne. He liked to call F16s "Jarts" because they were having issues with cracked wings at the time.
So regardless of legality, many things can be Jarts.
Originally it was planned on being a balance to the Eagle, which was (is) $$$$$$$$$$